Example embodiments relate to memory devices, and more particularly to semiconductor memory devices, memory systems including the same and methods of operating memory systems.
In general, a volatile memory device, such as a dynamic random access memory (DRAM), requires a refresh operation to maintain stored data. Therefore, a memory controller periodically provides refresh commands to a volatile memory device to refresh the memory device in a normal access mode.
However, as a density of a memory device increases, the refresh commands consume more power and decrease the efficiency of a command bus.